Field of the Invention
The invention is in the field of electric circuit "off" and "on" switches actuated in response to pressure differences, particularly for use with pressure or vacuum forming bags, and of small size, economical cost and ready adaptation to a particular environment.
A typical environment for the device is in connection with a vacuum bag utilized in curing composite laminates especially for aerospace use. The composite laminate is, for example, an impregnated fiberglass cloth put against a suitable mold, the cloth being forced to take the contour of the mold by either a pressure bag or a vacuum bag. A number of the thimble-shaped button actuators or responders are positioned inside a bag extending substantially horizontally over a panel to be cured. The bag is evacuated and the actuator responders correspondingly collapse and so indicate when the vacuum is at a predetermined value or is complete. Should there be a leak, some of the actuators or responders near the leak lose contact and afford a corresponding indication. Similarly, if the bag operates under pressure against a surface, actuators or responders are interposed between the bag and the surface and collapse to indicate a preselected pressure. The actuators or responders can easily be changed to respond to vacuum or subatmospheric pressures and for relatively high pressures. A representative thimble-shaped actuator or responder is described in the accompanying description and is shown in the accompanying drawings.